Review Question - QID 214297

This patient sustained a posterior hip dislocation. Of the answer choices listed, the fracture pattern seen in Figure C would be appropriately managed with EUA to assess hip stability.

Posterior wall fractures are the most common type of acetabular fracture. Management of posterior wall fractures is dictated by the extent of posterior wall involvement, with those involving >40-50% best treated with ORIF. Management of fractures involving 20-40% of the posterior wall, on the other hand, should be based on hip stability. As suggested by Tornetta, assessment of hip instability with dynamic stress views is helpful to determine which posterior wall fractures are unstable and therefore require open reduction and internal fixation. Protected weightbearing may be employed if the hip is stable; however, hip stability must be determined first.

Tornetta performed a study to assess the use of dynamic stress views in the non-operative management of acetabular fractures. He found that the use of dynamic stress views in determining the need for ORIF was effective, leading to good or excellent results in 91% of cases. He concluded that dynamic stress views can identify subtle instability in patients who would normally be considered for non-operative treatment.

Moed et al. performed a retrospective study to evaluate the role of CT in predicting hip stability in posterior wall fractures of the acetabulum. They analyzed 3 methods of calculating posterior wall fracture fragment size on CT and compared it to findings on EUA. They found that the alternative method (which measures fragment size at the level of the largest posterior wall deficit) was more accurate than the Calkins method (which measures the smallest amount of intact acetabular arc) and the Keith method (which measures fragment size at the level of the fovea). However, given the low risk of EUA and the inherent problems making CT measurements, they concluded that dynamic fluoroscopic stress testing under general anesthesia should be the preferred method for the determination of hip stability status after posterior wall fractures of the acetabulum.

Calkins et al. performed a study to assess the efficacy of CT in predicting hip stability based on measurements of the percentage of remaining posterior acetabulum. They found that all hips with <34% of the remaining posterior acetabulum were unstable, while those with >55% were stable. They concluded that a simple linear measurement of the remaining posterior acetabulum on CT can be done easily by a physician and can provide a means of predicting hip stability for individual patients.

Figure A is an AP radiograph of the right hip demonstrating a posterior hip dislocation. Figure B is an axial CT of the right hip demonstrating a posterior wall fracture with intraarticular fragments. Figure C is an axial CT of the right hip demonstrating a posterior wall fracture involving > 20% of the posterior wall. Figure D is an axial CT of the right hip demonstrating a posterior wall fracture involving > 40% of the posterior wall.

Incorrect Answers:
Answer 1: Protected weightbearing would be inappropriate for a posterior wall fracture with intraarticular fragments.
Answer 2: EUA would be inappropriate for a posterior wall fracture with intraarticular fragments.
Answer 3: Posterior wall fractures involving 20-40% of the posterior wall may be treated with protected weightbearing; however, EUA to assess for instability is recommended prior to making the final decision to proceed with non-operative treatment.
Answer 5: Open reduction internal fixation is indicated in unstable fractures such as posterior wall fractures involving >40-50% of the posterior wall.